The Democrats' plan for keeping the Senate? Repeat their 2012 message

Senate Democrats this week laid out their legislative and political agenda for this year, making it clear they hope to replicate the electoral success they saw in 2012 by focusing on economic issues that impact the middle class. They expect their economic message to trump the Republicans' large focus on Obamacare.

"We picked up seats in the Senate, we carried the presidency by a large amount" in 2012, Sen. Chuck Schumer, D-N.Y., said. "The American people, the majority aren't affected by Obamacare. They want to hear what we're going to do for them -- just go back and look at the 2012 election."

It's unclear whether Democrats will be able to sufficiently mobilize their 2012 supporters -- the CBS News poll released this week shows that Republican voters are clearly more energized about this election. What's more, Senate Democrats this year are defending seats they won in 2008 -- a breakthrough year in which Democrats won eight seats, the most they'd won since 1986.

"They won in a lot of red states that are doing to be difficult to defend this year," RealClearPolitics national political reporter Scott Conroy said in a conversation with CBS News elections director Anthony Salvanto. Democrats have to defend seven Senate seats in states that Mitt Romney carried, he pointed out, while they have only two clear opportunities to pick up seats (in Georgia and Kentucky).

"In the sixth year of a presidency it's... very tough for that president's party to win in midterm elections," Conroy added.

That's especially true given the coalition that Democrats built in 2012, notes Geoffrey Skelley of the University of Virginia's Center for Politics. Young people played a crucial role in President Obama's re-election, but data shows that for more than three decades, younger voters don't turn out for midterm elections the way they do for presidential elections.

Braley's gaffe in Iowa: One seat Democrats could have trouble defending is in Iowa, where Democratic Sen. Tom Harkin is retiring. The likely Democratic nominee, Rep. Bruce Braley, didn't do himself any favors this week when he was caught on camera at a Texas fundraiser criticizing Sen. Chuck Grassley, R-Iowa, for being just a "farmer from Iowa who never went to law school."

Braley apologized for the comment, but Republicans seized the opportunity to slam Braley for talking down to Iowa farmers. The National Republican Senatorial Committee, the Senate GOP's campaign arm, launched robocalls urging voters to "tell Bruce Braley to stop insulting Iowa farmers and that a law degree doesn't equal success." A conservative group called Priorities for Iowa is running an ad urging voters to tell Braley, "We'd rather bet the farm on Grassley than a bunch of trial lawyers from Texas."

Braley this week could take consolation in new endorsements from progressive Sen. Elizabeth Warren, D-Mass., and the grassroots group the Progressive Change Campaign Committee. In an email to PCCC supporters, Warren called Braley a strong voice for working families.

A Palin endorsement in Iowa: At the same time, one of the prospective GOP candidates in Iowa received her own high-profile endorsement.

Iowa state Sen. Joni Ernst, ran a memorable ad in which she recalled how she spent her youth castrating hogs. "Washington's full of big spenders," she says at the end of the ad. "Let's make 'em squeal."

Former Alaska Gov. Sarah Palin subsequently endorsed Ernst with a mention of the humorous ad. "Any question about the type of Senator Joni will be?" Palin wrote on her Facebook page. "Check out her first ad -- she makes it pretty clear."

Ernst is one of five Republicans running in the Senate primary, but a clear frontrunner has yet to emerge. A day after Palin issued her endorsement, the Citizens United Political Victory Fund announced its support for radio host Sam Clovis.

McConnell's basketball ad blooper: Senate Democrats think they could pick up a seat in Kentucky, where Senate Minority Leader Mitch McConnell is in one of his most challenging re-election campaigns ever.

McConnell's Democratic opponent, Kentucky Secretary of State Alison Lundergan Grimes, seized another moment to attack the Republican leader this week after the McConnell campaign flubbed up a campaign video.

The McConnell video featured footage of various patriotic scenes, including basketball players in blue and white uniforms -- presumably the University of Kentucky Wildcats. It turns out, though, that the players were from North Carolina's Duke University.

"After 30 years in Washington, DC, Mitch McConnell has clearly lost touch with Kentucky," Grimes' campaign said in a statement. "It turns out he has been in Washington so long he does not even know the difference between Kentucky and Duke basketball."

Schatz ad in Hawaii: The primary in Hawaii isn't until August, but Sen. Brian Schatz, D-Hawaii, is already up with his first ad, emphasizing his support for Social Security and his multicultural family.

"George and Ping live with us," Schatz says in the ad, referring to his wife's parents, "and Social Security has been there for George ever since his eyes gave out, ending his 30 years running the kitchen at Kwok's Chop Suey."

The Democratic senator is staking out a position to the left of his primary challenger, Rep. Colleen Hanabusa. Showcasing his Chinese-American in-laws could also help the senator, given that race is often a factor in Hawaii politics.