WASHINGTON - How early will America know if it's a Republican romp or if Democrats somehow minimized their damage? There should be plenty of clues this evening - and long before bedtime.

Final results in some states might not be known for days. But trends could be evident from the Midwest and South - especially from Indiana, Kentucky and West Virginia - even before most of the nation has finished dinner.

Six states have polls that close at 4 p.m. PDT, and 16 more close by 5 p.m., featuring plenty of telling races in the East and Midwest. First up: Indiana, Kentucky, South Carolina, Georgia, Virginia and Vermont, offering the first hard evidence of just how big a night it's going to be for Republicans.

Not even their mothers expect the Democrats to gain ground. It's just a question of whether they fall back or over a cliff.

If the GOP can unseat Democratic Rep. Baron Hill in Indiana's always-hard-fought 9th congressional district, for example, that's a good sign for the expected Republican takeover of the House. And if they can capture all three seats they've got an eye on in Indiana, that could well signal a GOP hurricane.

On the other hand, if Democrats hold their ground in Indiana, and if their Kentucky Senate candidate, Jack Conway, can beat back Republican Rand Paul, it could be an early indication that GOP gains won't challenge the record books and that the tea party is serving weak brew.

A few tips on what to watch as the returns roll in tonight (all times are PDT):

Expectations are high that Republicans will pick up at least the 40 seats they need to retake control of the House after four years of Democratic rule. That should start in the Midwest.

In Ohio, where polls close at 4:30 p.m., six Democratic-held seats are in jeopardy. In Pennsylvania and Illinois, where polls close at 5 p.m., 10 more are at risk.

If Midwestern incumbents such Joe Donnelly in Indiana and John Boccieri in Ohio fall, Republicans are probably headed for huge gains nationwide. Measure Democratic resilience if the party manages to hold on to a pair of imperiled Georgia seats, and if Rep. John Spratt can win a new term in South Carolina.

Worth watching in Florida (a 5 p.m. poll close): a rematch between Democratic Rep. Ron Klein and Republican Allen West. A loser two years ago, West rides anti-incumbent sentiment and is easily outspending his opponent.

Even if Republicans demonstrate early strength tonight, it will take time for them to lock in enough districts to ensure a GOP majority. That's because the West Coast states of California, Washington and Oregon are home to 67 House districts. In 2006, it was 1 a.m. before it became clear that control of the House had passed from Republicans to Democrats

SENATE

It would take a true blowout for Republicans to pick up the 10 Senate seats they need for control. The first should be an easy one, in Indiana. But if Paul can't keep Kentucky in the GOP column, it would be a sign of strength for Democrats and a symbolic setback for the tea party activists.

Republicans should have an easy time holding onto one of their own vacant seats in Ohio, where former Republican Rep. Rob Portman is favored. But keep an eye on West Virginia, another 7:30 poll close state, where Democratic Gov. Joe Manchin and Republican millionaire industrialist John Raese are tussling over the seat long held by the late Democrat Robert Byrd. A Republican victory there could keep alive GOP hopes of a majority.

Three-term Sen. Blanche Lincoln could be the first Senate Democratic incumbent to fall, when polls close in Arkansas at 5:30 p.m.

Polls close at 7 p.m. in the most closely watched race of the night: Senate Majority Leader Harry Reid's battle in Nevada against tea party favorite Sharron Angle.

Even if Republicans show huge strength, the nation still could go to sleep tonight with unanswered questions about the makeup of the Senate: Polls don't close until 10 p.m. in Alaska, where it could take days or weeks to determine the winner of a three-way race for Republican Sen. Lisa Murkowski's seat.

How long could the suspense drag on?

In 2006, it took until 5:30 p.m. the day after the election to determine that Democrats had taken control of the Senate from Republicans. And in 2008, it was nearly eight months after Election Day before it was determined that Democrat Al Franken had won Minnesota's Senate race, giving Democrats control of their 60th seat in the Senate, exactly the number needed to overcome a Republican filibuster.

GOVERNORS

For all the focus on Congress, there will be plenty of suspense over how big a real estate-grab the Republicans can manage in governors' mansions around the country.

South Carolina will offer an early measure tonight of tea party strength: Republican Nikki Haley trailed for months before Sarah Palin's endorsement and a tea party surge helped her nail the GOP nomination. Now she's favored over Democratic state Sen. Vincent Sheehen.

Over the next few hours, results will roll in for the blue-state Northeast, where Democrats are facing tough GOP challenges in Massachusetts, New Hampshire, Vermont, Maine and Connecticut. If Democratic Gov. Deval Patrick goes down in the liberal bastion of Massachusetts, it's a sign that the tea party fury over taxes and big government is spreading far and wide.

There's plenty of suspense in Florida, with a 5 p.m. poll close, in the battle between Republican businessman Rick Scott and Democrat Alex Sink, the state's chief financial officer.

Close contests are expected in late poll closing states Oregon and Hawaii. And polls don't close until 8 p.m. in California, where billionaire businesswoman Meg Whitman and former Gov. Jerry Brown are vying to replace outgoing Republican Gov. Arnold Schwarzenegger.

This isn't a presidential election year, but there will be plenty of 2012 tea leaf reading Tuesday night, especially when Western results start flowing in.

Most prominently among GOP hopefuls, Sarah Palin has endorsed numerous Republicans, and if they have a good night, so will she.

As for President Barack Obama at midterm, his grade will rely largely on the outcome of the fight for control of Congress. But his re-election campaign also will be affected by the result of gubernatorial races in states like Ohio, Iowa, Florida and his home state of Illinois.

Associated Press writers Liz Sidoti, David Espo, Nedra Pickler, Tom Raum and Julie Hirschfeld Davis in Washington contributed to this report.