WASHINGTON — The Senate Republican tax bill, which had appeared to be cruising to victory, suffered a setback late on Thursday as lawmakers were forced to contemplate significant changes, including future tax increases, to help pay for the legislation.

The bill had gained momentum in the morning when it picked up a key swing vote. But it came to a grinding, if temporary, halt, as senators scrambled in the early evening to find ways to raise several hundred billion dollars after some members objected to moving forward without a plan to safeguard against ballooning the deficit.

Lawmakers are now considering alternatives, including reinstating the alternative minimum tax on some corporations and wealthy individuals, and raising the corporate rate above 20 percent after some number of years. A final vote on the bill is expected on Friday after a series of amendments are considered.

The push to raise money came after an analysis by the congressional Joint Committee on Taxation found that the tax cuts would not pay for themselves by generating enough revenue through economic growth to offset the tax cuts, as Republicans have claimed, but would instead add $1 trillion to budget deficits over the next 10 years.