WASHINGTON – The Senate on Tuesday voted to relax a long-standing ban on bringing loaded guns into national parks, an outcome that underscored continuing divisions among Democrats over the politically charged issue of regulating firearms.

The vote was 67-29, with 27 Democrats and one independent joining 39 Republicans to approve an amendment overturning federal rules that require gun owners to carry their firearms unloaded and stored while visiting national parks. Instead, states would set policy within their own borders, even on federal lands.

The measure was approved as an amendment to an unrelated bill, a major effort to impose new restrictions on credit card companies that is expected to be approved by the Senate by week’s end.

The wide margin of support might not ensure the success of the gun amendment, acknowledged Sen. Tom Coburn, R-Okla., principal sponsor of the amendment. He said his proposal would likely be dropped when a conference committee meets to iron out differences between the House and Senate bills.

But he plans to revisit the issue in future bills, and the vote was the latest evidence that many Democrats remain wary of challenging the gun lobby.