Republican presidential candidate Ted Cruz tried to pick up more delegates in Colorado as front-runner Donald Trump stayed in his home state to focus on New York's all-important April 20 primary.
On the Democratic side, Bernie Sanders picked up another win in Wyoming's caucuses, but both the Vermont senator and rival Hillary Clinton were campaigning in New York.
The Wyoming vote was a draw from a delegate perspective: Sanders and Clinton each picked up seven.
Cruz hoped to add to his edge in Colorado over Trump when 13 more delegates were to be chosen at the state's Republican convention.
The Texas senator already had locked up the support of 21 Colorado delegates and visited the state to try to pad his numbers there. It takes 1237 delegates to win the nomination at the Republican national convention in July in Cleveland.
Keeping up his tussle with Trump over values, the ultraconservative Cruz told the Colorado crowd it's easy to talk about making America great again - "you can even print that on a baseball cap" - referring to Trump's campaign slogan, but that the more important question is which candidate understands "the principles and values that made America great in the first place".Trump holds a wide delegate lead nationally, but there seems to be a real chance no one will claim a majority of Republican delegates before the convention. A contested convention offers Cruz the best chance to secure the nomination.
Trump left the Colorado convention to his organisers, and spent about a half-hour touring the National September 11 Memorial and Museum in lower Manhattan.
The billionaire businessman, who makes much of the heroism of New Yorkers after the 9/11 attacks, left without speaking to reporters who were invited along for the visit. He plans to hold a rally in Rochester in upstate New York.
Trump's campaign issued a statement describing the site as "symbolic of the strength of our country, and in particular New Yorkers, who have done such an incredible job rebuilding that devastated section of our city".
It added: "This is what 'New York values' are really all about," a not-too-veiled poke at Cruz, who has taken heat for his earlier criticism of "New York values".
Democratic presidential hopefuls, too, were focused on New York's big trove of delegates even as Wyoming gave its nod to Sanders over Clinton.
Sanders got word of his Wyoming win from his wife, Jane, midway through a rally in the New York City borough of Queens. A raucous cheer went up from the New York crowd.
Clinton has 1287 delegates based on primaries and caucuses to Sanders' 1037. When superdelegates, or party officials who can back any candidate, are included Clinton has amassed even more delegates: 1756 compared to 1068 for Sanders. It takes 2383 delegates to clinch the Democratic nomination.