Much like Todd Akin in Missouri, tea party Republican Richard Mourdock is collapsing in the Indiana Senate race, thanks to his controversial remarks on rape and pregnancy. The latest poll to measure the race — from Indiana’s Howey politics — shows Mourdock with an 11-point deficit against his Democratic opponent, Joe Donnelly. Eighty-seven percent of Indiana voters were aware of the remark, and 40 percent said it made them less likely to support the Republican Senate candidate. Mourdock’s favorables are practically drowning — only 30 percent hold a favorable view of him, compared with the 49 percent who don’t — and Donnelly holds 47 percent support from voters in the state. If this holds, Democrats will have picked up a seat in one of the country’s deep-red states.

This gets to one of the striking things about the Senate picture this year: It’s possible — and at this point, likely — that Democrats will maintain or grow their Senate majority and move it further to the left. In Hawaii, the Senate Democratic primary — to replace outgoing Sen. Daniel Akaka — was won by Rep. Mazie Hirono, one of the most liberal members of the House. Using DW/Nominate — which places all members of Congress on a scale of –1 (most liberal) to 1 (most conservative) — it’s easy to see that Hirono, at a score of -.555 is slightly more liberal than Akaka, who holds a score of -.444. The same goes for Chris Murphy in Connecticut, who is more liberal than Joe Lieberman, and Tammy Baldwin in Wisconsin, who — if she wins — will be substantially more liberal than outgoing Sen. Herb Kohl.

When you combine this with the likely pick-up in Indiana — and the elections in Virginia, Florida, Missouri, Montana and Ohio — where Democrats will maintain the status quo, it makes for a Senate that’s far more liberal than the one that exists. The same goes for if Democrats make upsets in Nevada and Arizona, where they’re fighting tough but winnable races against favored Republicans. If he wins, Arizona’s Richard Carmona is likely to enter the Senate as a Blue Dog. But by replacing Jon Kyl — one of the most conservative members of the Senate — Democrats will have substantially shifted the center of ideological gravity.

What does this mean for 2013? If President Obama wins the election, liberals will have a better shot at stopping any “grand bargain” that makes regressive cuts to Social Security and Medicare. And if Romney wins? He’ll have to negotiate with a more liberal Democratic caucus, which means, in effect, that some promises of his campaign — large cuts in spending and taxes — will have to be moderated, or go unfulfilled.

Jamelle Bouie is a staff writer at The American Prospect , where he writes a blog .