The Republican majority on the 18-member panel was behind Judge Roberts. But his position became even more secure when Patrick Leahy, the senior Democrat on the committee, said he would vote in favour.
This is despite complaints by Democrats that Mr Roberts, who would replace the late Chief Justice William Rehnquist, was anything but forthcoming during testimony to the committee on his views on issues such as abortion and the relationship between religion and the state.
The Roberts confirmation process has produced a rare victory for President Bush, and left the Democrats in disarray. Despite some planned opposition when the nomination comes to the Senate floor on 29 September, several of the 44 Senate Democrats plan to support the nominee. He is likely to be confirmed with a majority of 65 or more of the 100-strong chamber.
But Mr Bush's next nominee, to replace Sandra Day O'Connor, faces a much rougher ride. Ms O'Connor was a key swing vote on a court that frequently split 5 to 4. If Mr Bush tries to tilt it to the right with an unabashedly conservative nominee, Democrats will put up fierce resistance.Reuse content