Republicans have distinct advantages in Senate races this year, including President Obama’s low job ratings, the number of vulnerable Democrats, and an unhappy national mood. But there’s another advantage: the generally high quality of their candidates. This wasn’t the case in 2010 and 2012, when Republicans blew chances to capture the Senate.

Strong candidates aren’t everything in elections. Money and the political landscape matter. And in a landslide, even poor candidates are swept into office. But as a rule, the better the candidates, the better the prospects for winning. This is especially true in national elections, where candidates get greater scrutiny.

What makes candidates “top-tier,” in the jargon of politics? They tend to be disciplined, quick-witted, have a credible message, don’t say absurd or unnecessarily provocative things, can raise money, and deal effectively with the media. It doesn’t hurt to be likeable, either.

In 2014, Republicans must gain six seats to take Senate control. And they’ve made this easier for themselves by dodging bullets in three Republican-held seats–Georgia, Kentucky, Mississippi. In those states GOP candidates that Democrats believed would be the easiest to beat were themselves defeated in the primaries.

In Georgia on Tuesday, businessman David Perdue won a Republican runoff against Rep. Jack Kingston and now faces Democrat Michelle Nunn in November. Democrats had hoped her GOP opponent would be either Rep. Paul Broun or Rep. Phil Gingrey, but both were eliminated in the primary. Perdue, the successful CEO of Dollar General stores, will be tough to beat in red-state Georgia.

In Kentucky, Senate minority leader Mitch McConnell was challenged by businessman Matt Bevin. Conservative groups spent heavily on TV ads to help Bevin, but he lost overwhelmingly in the primary. That gave McConnell a lift. Once seen as having no better than a 50-50 chance of defeating Democrat Alison Lundergan Grimes, he’s now the favorite.

In Mississippi, Senator Thad Cochran finished second to state senator Chris McDaniel in the primary, then won the runoff with the help of crossover votes by black Democrats. The clash left bad feelings among McDaniel voters, but Cochran should be able to handle Democrat Travis Childers. Democrats figured their only chance of winning was against McDaniel.

To win six or more Democratic seats, Republicans start with the best possible candidates in West Virginia (Rep. Sherry Moore Capito), South Dakota (former Gov. Mike Rounds), and Montana (Rep. Steve Daines). These open Democratic seats are regarded as near-certain GOP takeovers, but they wouldn’t be if Republicans were stuck with second-tier candidates or worse.

Then there are the four red states with Democratic incumbents–Louisiana, Arkansas, North Carolina, and Alaska. Once again, Republicans are blessed with able, attractive candidates. As a result, all five races are tossups or lean Republican. The Alaska primary isn’t until August 17, but I’m assuming former state attorney general Dan Sullivan will be the nominee. He’s already tied in polls against Democratic Sen. Mark Begich.

In Louisiana, Rep. Bill Cassidy, a doctor, is the strongest Republican opponent that Democratic Sen. Mary Landrieu has ever faced. And Louisiana also gets redder in every election. Cassidy has consistently held a small lead over Landrieu in polls.

Democratic Sen. Mark Pryor didn’t have a Republican opponent six years ago. Since then, Arkansas has trended Republican more than any other state. The Republican candidate is Rep. Tom Cotton, a Harvard graduate and Army veteran of Iraq and Afghanistan. This race is rated a tossup, but Republicans believe the staggering unpopularity of President Obama in the state should help Cotton win. He has led Pryor in recent polls..

The reelection campaign of Democratic Sen. Kay Hagan in North Carolina is backed by liberal groups and out-of-state money. And she looks stronger than she did a few months ago. Republicans chose state House Speaker Tom Tillis to run against her. He trails slightly in polls but has a solid shot at ousting her.

There are two states with incumbent Democrats where Republicans have strong candidates but the race hasn’t jelled yet. In New Hampshire, former Massachusetts senator Scott Brown is running against Democratic Sen. Jeanne Shaheen. In Virginia, former Bush White House adviser Ed Gillespie is challenging Democrat Mark Warner. Both are long shots at the moment, but good candidates often find a way to close the gap with their rival quickly.

And then we have Colorado and Iowa. Republicans were in despair in Colorado because they saw Democratic Sen. Mark Udall as beatable, but they lacked a candidate likely to beat him. Once Republican Rep. Cory Gardner was persuaded to run, that changed. Gardner was instantly labeled top-tier. He and Udall are roughly tied in polls.

Iowa is where Democratic Sen. Tom Harkin is retiring and Rep. Bruce Braley was installed as his likely successor. Not any more. That was before state senator Joni Ernst surged to victory in the Republican primary. She has stirred excitement and Braley hasn’t. Polls have them tied.

Republicans haven’t been this fortunate in candidates in years. And they indeed need superior candidates. In the past five elections, they’ve defeated only three sitting Democratic senators, ten in the past decade. To win the Senate this year, they’ll have to do better.

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