Why is Sen. Mary Landrieu (D.-La.) playing the race and misogyny card in the final days before the midterm elections? Why is Senate Democratic leader Harry Reid’s PAC running ads in North Carolina linking Republican Senate candidate Thom Tillis to the death of Trayvon Martin? Why is Sen. Mark Udall (D.-Colo.) so obsessively focused on abortion and contraception that he has earned the moniker “Mark Uterus”?

Because the elections have become a referendum on President Obama — and thanks to Obama’s sagging popularity, Democrats have given up on winning over independents and are desperately seeking to mobilize their dispirited base.

Democrats are in much the same bind today that Republicans found themselves in during the 2006 midterm elections, when President George W. Bush’s sinking poll numbers helped Democrats take control of the House, the Senate and a majority of governorships and state legislatures from the GOP.

Right before the 2006 elections, Bush’s approval rating among independents was just 31 percent. This meant that if Republicans candidates in tight races wanted to win these independents over, they had to distance themselves from Bush.

The problem with that approach was that the GOP base was intensely loyal to the president. Bush’s approval rating among Republicans was a solid 77 percent. This meant that if Republicans candidates distanced themselves from Bush, they would alienate the core voters they needed to come out for them on Election Day.

They were trapped.

Democrats have an even tougher challenge this year than Republicans faced eight years ago. Obama is just as unpopular with independents as Bush in 2006, but according to a CBS News poll his approval rating among the Democratic base is just 66 percent. Moreover, according to Gallup, only 25 percent of Democrats are extremely motivated to vote this year — compared with 44 percent of Republicans in 2006. So Democrats have to persuade their own unenthusiastic base to turn out and vote. But the more they try to persuade their base, the more they alienate the center.

Case in point is Landrieu’s decision last week to blame race for President Obama’s unpopularity in Louisiana and to absurdly claim that she faced an uphill challenge in her reelection campaign because she was a woman (in a state that has elected her to the Senate three times). This is clearly a last-minute Hail Mary play to energize women and African American voters. But Landrieu’s comments have also surely offended independents (and much of the rest of the Louisiana electorate for that matter), whom she has essesntially declared to be women-hating racists.

Of course, Republicans don’t deserve all the credit for putting Democrats in this bind. Obama certainly helped them along the way. Democrats would have loved for Obama to spend his time at closed-press fundraisers so that they could focus their campaigns on local issues. But Obama kept inserting himself into the conversation, declaring recently that “I am not on the ballot this fall . . . But make no mistake: These policies are on the ballot. Every single one of them.” Those comments made every vulnerable Democratic Senate candidate in the country cringe. The last thing they want is for these elections to be about Obama’s policies — from the Islamic State to Ebola to the economy to Obamacare.

With the Democrats trapped by Obama, their base depressed and the electoral map tilted in the GOP’s favor, we should be in for a big Republican victory Tuesday. But the one unknown of the 2014 midterms is the ground game. In the 2012 presidential race, polls suggested the election would be close, but the Obama campaign’s groundbreaking data-mining and voter turnout effort — code-named “Operation Narwhal” — turned the election into a blowout. Republicans kept blabbering about momentum, while Democrats were methodically turning out the vote.

It is unclear how much Republicans have been able to close the data-gap in the past two years and whether Democrats will be able to replicate their 2012 turnout effort in a non-presidential election year. This much is certain: It will have to be one heck of a turnout operation to overcome the Democrats’ Obama trap.

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