WASHINGTON — The May 20 elections are the best evidence yet that Republicans are avoiding previous mistakes and improving their chances of controlling the Senate during President Barack Obama’s final two years in office.

GOP voters again chose solidly conservative nominees while rejecting the most extreme and outlandish types who led the party to painful losses in 2010 and 2012.

The simple way to view this year’s results, thus far, is to say “establishment” Republicans are outperforming tea party insurgents. That’s largely true. But it blurs the extent to which nearly all Republican candidates — including some who have been in Congress for decades — have shifted rightward to stay in step with ardently conservative voters who helped create the tea party in 2009 and still dominate GOP primaries.

The differences between tea party and non-tea party Republicans are shrinking. Often it’s merely tone and experience that separate them. Tone and experience matter, however, and Tuesday’s GOP voters chose the less bombastic and unpredictable conservatives in most cases.

In Kentucky, Senate Minority Leader Mitch McConnell easily dispatched tea party challenger Matt Bevin. As a 30-year Senator and party leader, McConnell is about as establishment as they come. He has predicted that he and other mainstream Republicans will “crush” tea party candidates this year.

Bevin initially excited anti-establishment Republicans. But his campaign eventually collapsed under rookie mistakes and McConnell’s overwhelming advantage in money, experience and organization.

In Georgia, Republican voters rejected the two most outspoken tea party proponents, Reps. Paul Broun and Phil Gingrey. They set up a July 22 Senate runoff between two men who constantly emphasize their conservative credentials but leaven their rhetoric by wooing corporate support: Dollar General CEO David Perdue and Rep. Jack Kingston claimed the top two spots Tuesday and now begin a two-month runoff campaign.

Establishment Republicans once feared that Broun, who called embryology and evolution “lies straight from the pit of hell,” would win the nomination and become the type of gaffe-prone, over-the-top candidate who killed great GOP Senate chances in Delaware, Indiana, Missouri and other states in 2010 and 2012.

In Oregon, Republicans chose pediatric neurosurgeon Monica Wehby, who supports abortion rights, to run against first-term Democratic Sen. Jeff Merkley this fall. Her opponents included state Rep. Jason Conger, who was endorsed by the Tea Party Nation and former presidential candidate Rick Santorum.

Arkansas’ two uncontested Senate primaries officially set up a fierce November showdown between two-term Democratic Sen. Mark Pryor and freshman Republican Rep. Tom Cotton.

The Republican elections continued earlier trends from states such as North Carolina. There, Republicans nominated state House Speaker Thom Tillis for the Senate, rejecting a tea party leader and a Baptist minister who were making their first runs for office.

North Carolina Democrats scoff at the notion that Tillis is “moderate,” citing his self-described “conservative revolution” in the closely divided state. There and in many other states, Democrats will say the GOP Senate nominees are too conservative. They are happy to see Republican leaders play down the differences between themselves and tea party activists, as House Speaker John Boehner, R-Ohio, did.

“Sometimes,” Boehner told reporters, “there’s not that big a difference between what you all call tea party and your average conservative Republican.”

Before mainstream Republicans get too excited about the Senate results, they might note that Democrats have solid, well-funded nominees waiting. Oregon’s Merkley and Arkansas’ Pryor — like North Carolina’s Sen. Kay Hagan — have proven they can win statewide elections.

In Georgia and Kentucky, where Obama hardly campaigned in 2008 and 2012, Democrats are banking on two women with well-known political names. Michelle Nunn of Georgia is the daughter of former Sen. Sam Nunn. Kentucky Secretary of State Alison Lundergan Grimes is the daughter of a long-time Democratic Party leader.

Republicans need to gain six net Senate seats to control the chamber. Losing either McConnell’s seat or the Georgia seat, which Saxby Chambliss is vacating, could kill those chances.

Nunn would rather have drawn Broun as her opponent. And Grimes would have been ecstatic to face Bevin rather than McConnell.

So far, Republican primary voters aren’t handing those types of gifts to Democrats. That suggests they’ve learned the hard lessons of 2010 and 2012, when non-mainstream nominees lost winnable races.

Now the question is whether all Republican candidates — not just Constitution-quoting tea partyers — have moved too far right for moderate voters in November’s general elections.

—-

Charles Babington covers Congress and politics for The Associated Press.