Republican White House hopeful Mitt Romney talked up his chances yesterday ahead of two critical primary contests, saying he expected a “huge” double win that would catapult him towards the nomination.

But the fact that either of tomorrow’s votes, in supposed Romney strongholds Michigan and Arizona, is in play actually reflects how tight the Republican nomination battle to take on President Barack Obama in November has become.

Mr Romney insisted yesterday that “the momentum is in the right direction” and said: “I’m convinced I’m going to become the nominee and we’ll be willing to take however long it takes to get that job done.”

Yesterday, he secured the key endorsement of Arizona Governor Jan Brewer, who told NBC’s “Meet the Press “It was a difficult decision, but I think Mitt is by far the person who can go in and win.”

Rick Santorum, a staunch Christian conservative, is surging after a trio of wins in Minnesota, Missouri and Colorado earlier this month and is now leading the former Massachusetts governor in national polls of Republican voters.

Mr Santorum, a former Pennsylvania senator, has launched a strong challenge in Michigan, where Mr Romney was born and his father was governor, and in Arizona, where a significant proportion of the electorate share Mr Romney’s Mormon faith.

But polls in the past week have showed Mr Romney steadily eating away at Mr Santorum’s lead in Michigan – the two are now locked in a virtual tie in the Midwestern state – and suggest Mr Romney could be pulling clear in Arizona. “I’m planning on winning here in Michigan and also in Arizona,” Mr Romney told “Fox News Sunday.” “Obviously, that will be huge for us if we’re able to do (so), particularly having come from so far behind here in Michigan.”

The candidates face a potentially decisive stretch in a presidential campaign that has seen several rivals emerge to challenge Mr Romney, the default frontrunner, only to fall back in the full glare of the media spotlight.

After tomorrow, Washington state votes on March 3. Ten states then vote at once on “Super Tuesday” on March 6, when almost one fifth of all the vital convention delegates are up for grabs.

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