Mitt Romney hasn’t won the Republican nomination — yet.

But Tuesday’s primaries in five key states will probably put the former Massachusetts governor within 300 delegates of the 1,144 necessary to clinch his party’s presidential nod.

Former Massachusetts governor Mitt Romney (R). (Jessica Kourkounis/Getty Images)

And according to excerpts of an address he’s expected to deliver in New Hampshire this evening, Romney will drive home in the strongest language yet his general-election argument against President Obama.

“To all of the thousands of good and decent Americans I’ve met who want nothing more than a better chance, a fighting chance, to all of you, I have a simple message: Hold on a little longer. A better America begins tonight,” Romney is expected to say.

“Four years ago, Barack Obama dazzled us in front of Greek columns with sweeping promises of hope and change,” Romney will say, according to his prepared remarks. “But after we came down to earth, after the celebration and parades, what do we have to show for three and a half years of President Obama?”

With polls showing a general election race that is expected to be tight from the start, Romney is wasting no time in making his case against Obama, who is expected to clinch the Democratic nomination after polls close Tuesday night.

Obama, too, has been gearing up for a tough general-election fight, with visits this week to three college campuses where he has sought to rekindle the enthusiasm of young voters, whose support he won overwhelmingly four years ago.

Also competing for the GOP nod are former House speaker Newt Gingrich (Ga.) and Rep. Ron Paul (Tex.), although neither is expected to pose a significant challenge to Romney’s prospects.

By delivering his primary-night speech in New Hampshire, Romney is marking the de facto beginning of the general election by bringing his campaign back to the state where he announced his presidential ambitions 10 months ago.

“After 43 primaries and caucuses, many long days and not a few long nights, I can say with confidence — and gratitude — that you have given me a great honor and solemn responsibility,” he will say, according to excerpts. “And, together, we will win on November 6th!”

The argument that Romney will make against Obama — that he has failed as a leader on the economy and other issues — is one that the former Massachusetts governor has made time and again on the trail. But Tuesday night, he is expected to use language sharper than he has in the past.

“Because he has failed, he will run a campaign of diversions, distractions and distortions,” Romney will say of Obama, according to the prepared remarks. “That kind of campaign may have worked at another place and in a different time. But not here, and not now. It’s still about the economy . . . and we’re not stupid.”

And in keeping with his campaign theme of “restoring America,” Romney will also pledge to return the country to an America that is “fundamentally fair.”

“We will stop the unfairness of urban children being denied access to the good schools of their choice; the unfairness of politicians giving taxpayer money to their friends’ businesses; the unfairness of requiring union workers to contribute to politicians not of their choosing; the unfairness of government workers getting better pay and benefits than the taxpayers they serve; and we will stop the unfairness of one generation passing larger and larger debts on to the next,” he will say.