Senate Minority Whip Jon Kyl plans to announce his 2012 intentions in February, and a decision by the Arizona Republican to retire could ignite a heated race for his No. 2 slot while unleashing significant changes within the GOP leadership.

Kyl said he is close to a decision on whether to seek a fourth term. But the Minority Whip is keeping close counsel — so much so that even many longtime Kyl supporters who otherwise expect him to run for re-election now believe retirement is a real possibility.

Should that be Kyl’s choice, the favorites to replace him as Whip in 2013 are Republican Conference Chairman Lamar Alexander (Tenn.) and National Republican Senatorial Committee Chairman John Cornyn (Texas), with Republican Policy Committee Chairman John Thune (S.D.) also viewed as a contender.

“The most viable would be John Cornyn because of his success at the NRSC, and he might have another good election cycle,” a former Senate Republican leadership aide said. “Also Thune, if he doesn’t run for president, and Lamar Alexander, who is very close with” Minority Leader Mitch McConnell (Ky.).

Alexander has strong relationships with both conservative and moderate Republicans, and he mounted a strong bid for Whip after the 2006 elections, losing a close contest to then-Sen. Trent Lott (Miss.). When Lott resigned from office a year later to go work downtown, Kyl got the post.

Cornyn has received high marks from his colleagues for his work at the NRSC. The Republicans picked up seven seats last cycle, overcoming initial predictions that the party would lose ground. And with 23 Democrats up in 2012 compared with only 10 Republicans, the GOP has a legitimate shot at capturing the majority.

Republican sources on and off Capitol Hill say that Cornyn, who served as Conference vice chairman before taking over the NRSC, could have the edge over Alexander if both were to run for Whip. That advantage could come from the support of Senators whom Cornyn helped elect in 2010 and those he would presumably aid in 2012. Either way, the Texan is expected to land in leadership in some capacity in 2013.

One Republican lobbyist who follows the Senate referred to Cornyn as the favorite to succeed Kyl if the Arizonan retires. Kyl’s departure could lead to a domino effect at the top of the Republican Conference and create openings that might interest several ambitious Senators.

Openings sometimes occur because of the rule that limits Senators to no more than six years in one leadership position, but the GOP Conference leader is exempted from this regulation.

Those viewed as ambitious include Sen. Bob Corker (Tenn.), a first-term lawmaker who is running for re-election next year. Corker has been mentioned by Republican operatives who monitor the Senate as a logical choice for NRSC chairman in the 2014 cycle, but he was tight-lipped about his desire to join leadership when asked.

Sen. Richard Burr (R-N.C.), who serves as Kyl’s Chief Deputy Whip, is seen as electable, depending on what position he might pursue. And GOP Sens. Tom Coburn (Okla.) and Mike Johanns (Neb.) are frequently mentioned as leadership candidates, although both have declined to pursue openings in the past and instead focused their efforts on legislation and committee work.

Among the newly elected Republicans, Sens. Kelly Ayotte (N.H.) and Rob Portman (Ohio) are seen as leadership material. Republican leaders have already tapped Ayotte in an unofficial capacity because of her ability to speak to women’s issues and showcased her as the lone freshman at their first press conference this year. Kyl picked Portman to serve on the Whip team, and the Ohioan commands the attention of his colleagues because of his experience serving in the administration of George W. Bush.

Republicans based in Washington, D.C., tend to believe that Kyl will run for re-election, particularly because he could become Majority Whip in 2013. But Republicans in Arizona, including Kyl supporters, are now less certain.

They initially believed that Kyl’s refusal to discuss his re-election plans so soon after the 2010 elections was related to his usual desire to take a break from politics and focus on legislating. In fact, Kyl has not been shy about expressing to reporters his disdain for such questions.

But Republican sources based in the Grand Canyon State now describe Kyl’s backers as “panicked” and being in a holding pattern as it relates to fundraising and everything else connected to a re-election bid. Kyl survived a strong challenge in 2006, a down year for the GOP, and is viewed as the overwhelming favorite to win re-election in 2012 should he run. Roll Call Politics rates his race Safe Republican.

“It has been widely discussed here that Kyl is not going to run,” a Republican consultant based in Arizona said.

Kyl said on Thursday, “I’m getting close to both a decision, and when, and I don’t know exactly when, but in February.”

Cornyn has an interest in Kyl running because open seats usually require more money and attention from a Congressional campaign committee at the expense of focusing on seats held by the opposition party. He told Roll Call he has not discussed the matter with Kyl or pressed him to run.

“It’s an enormously personal decision and so — maybe others feel differently, but I kind of feel like it’s not my place because I have to respect an individual decision,” Cornyn said, although he made clear he would prefer that Kyl stick around.

“Jon Kyl is one of our most effective Members.”