Washington ? When voting began Thursday on whether to advance President Bush’s immigration bill, Kansas Sen. Sam Brownback was among the first lawmakers to vote “yes.”

About 10 minutes later, Brownback switched his vote to “no.”

But don’t bother accusing the Republican presidential hopeful of flip-flopping – he says he did it on purpose.

“I wanted to signal that I support comprehensive immigration reform, but now is not the time, this is not the bill,” Brownback said.

Brownback explained that his “yes” vote initially was to “showcase” that reform is needed. The switch to “no” was because he didn’t think this was the right way to do it.

Spokesman Brian Hart confirmed that Brownback planned the switch all along, ever mindful that presidential candidates face a tough time explaining vote switches.

“You don’t go to the Senate floor to vote ‘yes’ and then vote ‘no’ in the John Kerry era unless you mean it,” Hart said, referring to the Massachusetts senator and former Democratic presidential nominee.

Kerry was accused of waffling in 2004 after he tried to explain his votes on funding the Iraq war. “I actually did vote for the $87 billion before I voted against it,” Kerry said.

The Bush campaign repeatedly used Kerry’s comments in television ads to back its claim that Kerry was a flip-flopper.

Brownback has shifted his position on the bill since last year, when he supported a Senate measure that would give millions of illegal immigrants a chance to become U.S. citizens. Brownback came under heavy criticism from conservatives who adamantly oppose the bill.

Now, Brownback says he favors a comprehensive approach to immigration reform that secures the border, provides interior workplace enforcement and establishes an effective guest worker program.

“I became convinced along with many of my colleagues on the floor that this version of the immigration bill was not, and would not become, the vehicle that would fix our broken system as I had hoped,” Brownback said.

Hart denies that Brownback has changed his position on immigration reform, saying the senator was hopeful that the bill last year would be improved in conference committee when Republicans were still in charge of Congress.