WASHINGTON — When the Senate Judiciary Committee voted in January on a bill that would reduce sentencing for nonviolent drug offenders, there was a stark divide in the votes.

The divide wasn't partisan.

The average age of the three Republicans who voted for the bill — Sens. Mike Lee, Rand Paul, and Ted Cruz — was 45.3 years old. The average age of the five Republicans who voted against the bill: 69.4 years old.

These days in Washington, there is a bipartisan coalition of lawmakers ready to change the U.S. criminal justice system, from changing drug laws and eliminating mandatory minimum sentencing to changing practices inside prisons like solitary confinement.

But standing in the way is a generation of older lawmakers who came of age politically during the 1980s and early 1990s when being tough-on-crime was a prerequisite for office.

"The issue is when you came of age on the justice issue and what your experiences have been," said Idaho Rep. Raul Labrador, a former criminal defense attorney elected as a Republican from Idaho in the 2010 tea party wave. "If you look at the 1980s, crime was so high that you had to be really tough on crime. But law enforcement has made some huge advances on how to combat crime and what they need to do."

Labrador is the sponsor of the Smarter Sentencing Act in the House — a bill that would change how drug sentences are handed down — and one of 13 Republicans backing the legislation. Ten of the Republican sponsors are less than 60 years old. Five are less than 50. That's young even for the tea party-era GOP caucus, which, according to 2011 Wall Street Journal calculation, averages in at 54.9. Twenty Democrats have signed on as co-sponsors.

"As a somebody who is a fiscal conservative and as somebody who understands the importance of these types of crimes," he said, "I think that's why you've seen a group of young conservatives saying, 'Hey, maybe we've been going about this the wrong way.'"

Advocates believe the generational politics play a part in preventing legislation from moving. Rolling back tough drug sentencing rules is seen by some as going squishy on crime — abandoning the very laws that helped get some older members elected and reelected in the first place.

"In the 1980s there was this feeling of 'If I support anything innovative on crime or anything other than massive incarceration, I'm going to get hit with a Willie Horton ad and I'm not going to get reelected,'" said Molly Gill, government affairs counsel for Families Against Mandatory Minimums, a group at the center of the fight for the Smarter Sentencing Act. "But now we're living in a totally different era."

The growing belief that the War on Drugs and its associated rise in the prison population has been an expensive failure has spurred on the younger generation of lawmakers. What the Smarter Sentencing Act does, according to advocates, is relatively minor in terms of policy, essentially cutting in half existing mandatory minimum sentences that range from five to 20 years, granting judges greater power to ignore minimum sentences, and giving inmates the right to have their sentences reviewed by a judge under new drug sentence rules established in the bill.

"This bill is so modest, and that's what's so remarkable about the opposition," Gill said. "This bill doesn't even get us out of the prison box ...This bill is still very much in the mentality that drug offenders go to jail. Under this bill, everyone still goes to jail. So in that sense, this is not a soft-on-crime bill."

But the Smarter Sentencing Act's tweaks to drug sentencing rules represent a huge shift in the politics of drugs — away from expanding prison populations and towards shorter sentences for nonviolent offenders — and therein lies the GOP split that could kill the bill.

"The American system is built to be deliberative," said Eli Lehrer, president of the R Street Institute, a libertarian-skewing think tank that supports a reexamination of the drug war, said. "I'm not that different from a lot of these people and obviously I hope that the Smarter Sentencing Act would become law. I support it. But I don't think the conservatives oppose it — or the liberals opposing it — are doing so out of bad motives."

Lehrer believes the Republican Party won't change until some of the fervent tough-on-crime types have left politics.

"The generational divide is enormously important," he said. "If somebody was originally elected at a time when many of their constituents'' number one complaint was crime, that's going to shape their political ideology for life, as it should."

Supporters of the Smarter Sentencing Act think its possible to get the bill passed with the current makeup of the GOP. They're out to change minds, and this week they lobbied members of Congress with the help of drug offenders granted presidential clemency shortening their sentences.

But even the bill's limited policy changes face a tough road in the House.

The man standing in the way is the 61-year-old chair of the Judiciary Committee is Rep. Bob Goodlatte of Virginia. He has declined to give the bill a committee hearing, the first step required for a vote by the full House. Last month, he told reporters he's not sold on the Smarter Sentencing Act or the larger effort to reevaluate the drug war that's behind it.

"I want to caution that we shouldn't jump to conclusions about what is right and what is wrong with the law yet," Goodlatte said of current sentencing guidelines for drug offenders, including mandatory minimums.

Advocates, still hopeful that Goodlatte will come around, wouldn't name him as the hurdle keeping the bill from coming to a vote. Labrador said Goodlatte told him in a conversation "a couple of weeks ago" that "we're going to have a hearing soon." Goodlatte's office did not respond to multiple requests for comment.

Labrador blames some of the difficulties he's had gathering Republican support for the Smarter Sentencing Act on President Obama, who is a strong ally of the sentencing movement. Labrador, like other conservative prison activists, steered clear of Obama's plan to reduce some drug sentences on his own through a massive clemency effort, managed by the Department of Justice. Labrador said the program sounds unconstitutional to him and said that Obama going it alone — even in a way that closely mirrors the outcomes Labrador hopes to achieve with the Smarter Sentencing Act — makes it very hard to convince Republican lawmakers to get on board.

"He's kind of incorporating part of his sentencing reform into his clemency...He's changing the policy before the law changes," Labrador said. "That makes it more difficult for people like me."

The administration, for their part, maintains its support for the legislation.

"This is commonsense, bipartisan legislation, and Republicans say they support it, so they should pass it," said White House spokesperson Matt Lehrich.

But House Republican opposition to the bill also comes from the prosecutor lobby, according to Labrador. Some believe long sentences are the key to reduced crime.

"The main concern that I hear are coming from advocates of our current sentencing system ... that having tough on crime sentences actually helps you reduce crime because you can use those tough sentences to get people to plea to lesser deals," he said. Labrador said prosecutors often bundle minimum sentences, telling accused they need to plea guilty and take some jail time or face decades behind bars. "You know, 'Talk to us about the crime or we're going to put you in prison for 30 years.' And the government should never have that much power over somebody's life. That goes against what our founding fathers wanted."

Labrador is convinced that the Smarter Sentencing Act will become law one day, but he's not optimistic about its chance of leaving the House by year's end.

Proponents in the House got a boost last week, however, when Wisconsin Rep. Paul Ryan came out in favor of the Smart Sentencing Act in an interview with The Daily Beast.

In the Senate, it's a slightly different story. Advocates and aides are willing to point the finger at who's responsible for slowing any big changes to the prison system.

Advocates are convinced Senate Majority Leader Harry Reid will put the Smarter Sentencing Act on the Senate floor before the end of summer, possibly before the end of June. But Senate Republican aides say Sens. Chuck Grassley and Jeff Sessions, a former attorney general of Alabama, are the men making it impossible to predict whether the bill will avoid filibuster.

"Sen. Grassley's views on this have been clear for years, and I think he's making those views known," Gill said. "His views are not in step with the times and we just have to keep emphasizing to people that this is an area where we have 30 years of experience with mandatory minimums and those 30 years don't paint a pretty picture."

Grassley aides did not respond to a request for comment on Gill's characterization of his views.

Despite the Republican hurdles in Washington, conservative supporters of sentencing efforts have a reason to be hopeful: the states. In red state after red state, Republicans now in total control of state governments have used their power to enact criminal justice policy changes that have drawn support from progressive groups like the ACLU and the NAACP. And it's not just young Republicans who are pushing the party to take a new approach to crime: Georgia's 71-year-old Gov. Nathan Deal is considered a model Republican by advocates when it comes to criminal justice issues. Legislative packages Deal has signed into law have saved Georgia millions of dollars and become a key part of his legacy.

Gill said she hopes the Republican experience with criminal justice shifts in the states will help older Republicans in Washington move closer to their younger colleagues.

"People who pass these reforms at the state level," she said, "they get reelected."