WASHINGTON — Wealthy donors to outside groups backing Republicans Mitt Romney and Newt Gingrich include a leading hotel magnate, a casino mogul and Romney's former partners at his private equity firm.

The donations to so-called super PACs are paying for TV ads that sometimes are dominating the GOP presidential nomination fight. The groups have spent or reserved time for millions of dollars so far on ads in New Hampshire and South Carolina, and at times have spent as much as the candidates themselves.

Many of the contributors will remain secret until later this month, when the PACs must report their finances to the Federal Election Commission.