Colorado may ask voters again whether 21-year-olds should be able to serve in the state Legislature.

The state Senate gave tentative approval Monday to a measure to lower the age of eligibility from 25 to 21. Supporters say the change could get more young people engaged in the political process.

But the measure faces an uphill battle.

The state constitution would have to be amended, which means the change needs more than a simple majority to clear the Legislature. A preliminary vote Monday was short of the needed threshold, so the measure needs additional support before clearing the Senate.

The measure would also have to pass the House and be approved by the governor before heading to voters. Colorado voters rejected lowering the age from 25 to 21 in 2008.