When did the election season begin?

This article originally appeared on Slate.

Labor Day was once the unofficial start to the fall campaign season, but now it's more like Angelina Jolie's marriage to Brad Pitt--a milestone in an engagement that has been going on so long it's hard to think of a time when it wasn't.

Labor Day was never a marker of the first moment of campaign activity, but a rough approximation of the time when the pace quickened. So when was that moment in this campaign? The answer depends on how you see this race unfolding, in a year where Republicans have tremendous national advantages and Democrats are trying to keep the races local. Here are a few possibilities of where to drop the needle:

The day after Election Day 2012: Republicans had a chance to retake control of the Senate in 2010 and 2012. After the second missed opportunity, strategists, wealthy backers, and other members of the GOP establishment focused on recruiting candidates who could unite the GOP coalition but who most of all were good politicians unlikely to make career-ending gaffes.

April 2013--Democrats launch Bannock Street Project: Both parties are boasting about their unprecedented efforts to turn out voters. That's another reason campaigns start earlier. As technologies and science of voter identification and mobilization have improved, the parties and their allies have started hunting down voters earlier and earlier. In 2001 the Republican National Committee boasted of a "72-hour task force" before Election Day. Now, the RNC boasts of its Victory 365 Program, a permanent grassroots field operation that will run all year long.

But Democrats face a higher turnout hurdle than Republicans. Voters that made up a key portion of Obama's winning coalition--single women, minorities, and young voters--don't usually participate as much in nonpresidential elections. That's why last spring, Guy Cecil, the executive director of the Democratic Senatorial Campaign Committee met with Senate Majority Leader Harry Reid and Sen. Michael Bennet to outline the Bannock Street Project, a $60 million, 10-state effort to reverse that historical trend. Named after the Denver field headquarters of Bennet's successful 2010 campaign, it will be crucial in keeping the Senate in Democratic hands.

Oct. 1--Launch day of Healthcare.gov: Perhaps the biggest reason campaigns start earlier than ever before is that super PACs, which raise mountains of money, can put ads on television early and keep them there. Campaigns, by contrast, must husband their resources, which are harder for candidates to raise. In advance of the launch of the open-enrollment period for federal health care exchanges, Americans for Prosperity launched ads targeting the Affordable Care Act. Then, when the website collapsed and some customers were not allowed to keep their insurance, as the president had promised, AFP started running television ads attacking Democrats for their support of Obamacare. "It was the earliest, most comprehensive ad campaign that we've ever seen," says Elizabeth Wilner, senior vice president of Kantar Media Ad Intelligence. "The ads didn't just dribble out. It was a well-organized, unprecedentedly funded ad campaign."

The ads and the extended collapse of the website put Democrats so on the defensive that Senate Majority PAC, the lead outside group defending them, had to launch its ad campaign early to beat back the assault. The airwaves have remained stuffed ever since.

President Obama's health care plan is not the white-hot issue it was late last year, but one lasting benefit Republicans have already banked from that time is the recruitment of good candidates in states that might not otherwise have been competitive. Strategists say that it was easier to persuade GOP Senate candidates Cory Gardner to run in Colorado and Scott Brown in New Hampshire because the ad campaign had so battered Democrats in those states. Those GOP recruits also knew from the money being spent on those ads that if they got in the race they'd have a big bank account behind them.

Dec. 1--The day healthcare.gov recovered: If Democrats are able to survive in this tough election cycle, it will be because they kept the election focused on their opponents and local issues instead of national ones. Though they have been tested on a range of national issues from the systemic problems at the Department of Veterans Affairs to foreign policy challenges, there was no greater national distraction for Democrats than the protracted collapse of the president's health care website. When the website started humming and the health care law moved from being such a contentious issue, the air cleared, and Democrats were allowed to focus on their own campaigns and local messages.

June 24--Sen. Thad Cochran beats Chris McDaniel in Mississippi's GOP primary runoff: "We thought McDaniel would be this year's Akin," says one top GOP strategist, referring to Todd Akin, the former Missouri Senate candidate. Akin's remarks about "legitimate rape" during the 2012 cycle not only sunk his chances, but tarnished the GOP brand in other races.

Despite this year's efforts to shut out exotic candidates, the campaign season started with seven Republican incumbents facing Tea Party challengers. All of those candidates were beaten back. In open seats, Republicans nominated candidates who were best positioned to win in a general election.

In many cases, the victors simply learned to appeal to Tea Party voters. In some cases, though, Republicans dodged a bullet. If Steve King had decided to run in Iowa, he would have been far more polarizing in that purple state than the current Republican nominee Joni Ernst, who is now neck-and-neck with her Democratic opponent. The worry with McDaniel was not that he would put Mississippi in play, but that his past comments about women and black Americans would have created problems for the party as a whole and energized those two key Democratic groups.

Labor Day has not lost its role completely in the modern campaign cycle. There are some structural reasons the race will change in the days to come. By law, television stations must offer the lowest available rate for advertisements to candidates in the last 60 days of a campaign, which means we'll start to see different kinds of ads on television. Debate season is also coming, which could mix up things. Partisans may have been locked up earlier than ever before because of absentee and early voting, which in some places starts well before Election Day, but last-minute undecided voters are also still out there. In close races, even a small number of them will matter. One strategist suggests that because the campaign has started earlier, last-minute voters are more turned off to the noise than ever, meaning they may not pay attention until October. (Columbus Day is the new Labor Day!) And, of course, there could always be a surprising last-minute national event that could throw the entire race into turmoil.

We won't know until after the election which one of these moments will emerge as the turning point that either changed control of the Senate or not. But once analysts and pundits fix on a reason, new campaign strategies will be launched for the next campaign, since strategies for the next campaign, like the Bannock Street Project, are born from the successes of the previous ones. Given the pace of things, those 2016 strategies will probably be launched not long after Election Day.