Republican Marco Rubio's potential defection over a tax credit for low-income parents has put a speed bump into GOP leaders' drive to push their big tax package through the Senate, but it's a complication that's likely to be resolved.

The Florida senator says he'll vote against the $1.5 trillion bill unless House and Senate negotiators expand the tax credit that low-income Americans can claim for their children.

That puts the Republicans' razor-thin margin in the Senate closer to the edge. The GOP leaders are straining to muscle the bill through Congress next week, handing President Donald Trump his first major legislative victory by Christmas.

The Senate turmoil erupted the same day that a key faction of House Republicans came out in favor of the bill, boosting its chances.

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