AP

CRAIG (COLORADO) MITT ROMNEY is poised to clinch the Republican presidential nomination after Tuesday’s Texas primary, a largely uncontested election that will formalise the former Massachusetts governor’s status as President Barack Obama’s general election challenger in November.

While Romney’s nomination has been virtually assured for a month, the day marks the culmination of several years of work, dating back to his unsuccessful 2008 presidential bid, and perhaps far earlier.

“It’ll be a big day tomorrow,” Romney told reporters aboard his campaign plane on Monday evening. “I’m looking forward to the good news.” But Romney’s focus on Tuesday will be in Colorado and Nevada, where he’s scheduled to court voters and donors and attend a Las Vegas fundraiser with celebrity real estate mogul Donald Trump.

The event comes amid fresh criticism from both Republicans and Democrats over Trump’s continued questioning of Obama’s citizenship.

Romney hasn’t condemned Trump’s false claims, an example of the candidate’s reluctance to confront his party’s more extreme elements.

Romney is making a delicate push to win over skeptical conservatives while appealing to moderates and independents who generally deliver general election victories.

On Tuesday, Obama’s campaign launched a new television commercial accusing Romney of failing to stand up to ‘the voices of extremism’ in his party.

The ad opens by showing 2008 Republican nominee John McCain brushing aside a woman who raised the citizenship issue at a town hallstyle meeting, and the commercial asks, “Why won’t Mitt Romney do the same?” Romney has been criticised on several occasions for failing to speak out against extreme rhetoric from his party. The reluctance stands in contrast to McCain, who once corrected a supporter who called Obama a Muslim.

Romney on Monday declined to condemn Trump’s latest suggestion that Obama was born in Kenya.

“I don’t agree with all the people who support me. And my guess is they don’t all agree with everything I believe in,” Romney told reporters. “But I need to get 50.1 percent or more. And I’m appreciative to have the help of a lot of good people.” Polling suggests that the election between Romney and Obama will be very close, ultimately decided by several swing states, Colorado and Nevada among them.

The Texas primary offers 152 delegates. Romney is just 58 delegates shy of the 1,144 needed to become the nominee.

Republican rivals Rick Santorum and Newt Gingrich already have endorsed Romney, while libertarianleaning Texas Representative Ron Paul has stopped actively campaigning. Gingrich is expected to attend the Trump fundraiser.

Romney’s meeting with Trump may generate more interest than his new grasp on the Republican nomination.

“I do not understand the cost benefit here,” conservative commentator George Will said over the weekend.

“The cost of appearing with this bloviating ignoramus is obvious, it seems to me.” Senior Romney aide Eric Fehrnstrom also declined to condemn Trump’s remarks in a recent interview.

“I can’t speak for Donald Trump but I can tell you that Mitt Romney accepts that President Obama was born in the United States,” Fehrnstrom said. “He doesn’t view the place of his birth as an issue in this campaign.” In the past, Romney was also slow to condemn conservative radio host Rush Limbaugh, who said a college student defending Obama’s contraception policy was “a slut.” At the time, Romney initially declined to weigh in on the issue before saying “it’s not the language” he would have used.

And Romney was initially silent on violent rhetoric from classic rocker Ted Nugent before a spokeswoman said Romney “believes everyone needs to be civil.