On the eve of the midterm elections, Democrats are widely expected to lose control of the House of Representatives. But will they hold onto enough seats to declare the midterms a modest success, or are they in for an all-out massacre? Here are four bellwether races that will help determine just how much ground Democrats will lose to the Republicans in the next Congress:

1. Indiana's 2nd District: A Democrat runs from his own party
In conservative northern Indiana, Rep. Joe Donnelly has adopted a strategy that is proving popular among Democratic incumbents facing formidable challenges — he's running as a critic of President Obama and House Speaker Nancy Pelosi. In one ad, Donnelly says he "voted against Nancy Pelosi's energy tax on Hoosier families." Instead of touting his own party's achievements, Donnelly has chosen to run "on Hoosier values, whatever those might be," says Melinda Henneberger at Politics Daily. So far, Donnelly's approach seems to be paying off; he leads in recent polls against Republican Jackie Walorski. But if he falls, it could be a sign that Democrats are in for a long night.

2. Virginia's 6th District : A "vulnerable" progressive on the ropes
Can a proud defender of unpopular Democratic legislation win in a red district? Virginia's freshman Rep. Tom Periello is "unapologetic, even tireless, in his defense of his votes for health reform, cap and trade, et al.," says Adam Sorensen at Time. But his enthusiasm has made him easy prey for Republican John Hurt's campaign, which has portrayed Periello as "nothing more than a lap dog for the job-killing Obama-Pelosi agenda." President Obama has plugged Periello's campaign several times recently, and plans to make a last-minute campaign visit, but Periello trails Hurt in all recent polls.

3. Florida's 8th District : Can a liberal provocateur survive?
Alan Grayson's history of incendiary remarks may be catching up with him. The polarizing freshman Democrat, whom George Will at Newsweek calls "America's worst politician," faces an uphill battle against Republican Daniel Webster, whom Grayson infamously labeled "Taliban Dan" in a campaign ad. Protesting against such tactics, Webster is now "refusing to be anywhere near Grayson prior to the election" — but that doesn't seem to be impacting his ascendant poll numbers.

4. New York's 19th District: Are Democrats losing the suburbs?
Democrats are having trouble hanging on to House seats north of New York City, says The New York Times, which shows that Republicans are on the verge of taking back seats they ceded in the Democratic wave elections of 2006 and 2008. A case in point is New York's 19th District, where polls show a dead heat between two-term Democrat John Hall and Republican Nan Hayworth, with one pollster saying that "this has the potential to be one of the closest races in the nation." If Hall is defeated, it will be a sign that Democrats are losing their grip on suburban voters — a demographic they can ill afford to give up. 

Sources: Time, The Washington Post, The New York Times, Newsweek, Daily Caller, Politics Daily, Bloomberg