(AP) - The Republican primary race is effectively over but Mitt Romney keeps piling up delegates and endorsements.

He was expected to tighten his lock on the GOP nomination by sweeping Pennsylvania, New York and three other northeastern states holding primaries Tuesday. They offer a combined trove of 209 delegates.

The presumptive GOP nominee campaigned in Pennsylvania on Monday with Florida Sen. Marco Rubio, often mentioned as a potential running mate.

He also picked up the endorsement of former New York City mayor Rudy Giuliani, a 2008 rival. Giuliani, who joins a long line of Republican luminaries to back Romney, said the former Massachusetts governor "won fair and square." The value of endorsements has long been debated. But generally, they're better to have than not. And in Romney's case, they help him demonstrate that he's solidifying his party's support.

No endorsements for Romney have yet come from vanquished rival Rick Santorum or from Texas Rep. Ron Paul and former House Speaker Newt Gingrich.

Santorum once hoped to break his losing streak with a home-state Pennsylvania win in Tuesday's primary. But amid discouraging polls, he bowed out April 10. He's widely expected to make the endorsement and may be waiting until closer to the convention in August in hopes of giving it more punch.

Gingrich did campaign actively ahead of Tuesday's primaries - in Delaware.

Cash short and deeply in debt, Gingrich picked it hoping for an upset and because of its proximity to the Washington D.C. area where he lives.

Paul has a base of diehard supporters and has had little trouble raising contributions. He told CNBC he has no plans to quit.

"You don't quit because you happen to be behind," he said. "You want to see how you do. And who knows? Maybe somebody will stumble."