After an initial burst of optimism, most lawmakers quickly grew skeptical of the $2 trillion infrastructure framework that President Trump and congressional Democrats proposed this past Tuesday.

Most doubters pointed to the incredibly high price tag and noted that neither side settled on a way to pay for the massive program: a higher gas tax, increased taxes on the wealthy, a user fee based on how many miles you drive?

But the bigger problem might be that lawmakers feel little incentive to support such a massive project because their constituents view Congress with such deep cynicism and doubt their cities and towns will see any benefits.

Voters tend to see big funding proposals, or large tax cuts, as a giveaway to powerful interests, things that benefit others. It would take years for the new highway exchanges, bridges and refurbished dams to get approved by federal agencies, and by then constituents won’t connect the dots to understand those projects came about because of congressional action a few years back.

This is part of the reason behind the push for the return of the once-hated E-word: earmarks.

“Yes — I’m talking about restoring earmarks, which I believe can be great instruments of good when done in a way that is fully transparent and accountable,” House Majority Leader Steny H. Hoyer (D-Md.) testified in March before a select committee tasked with recommending internal reforms.

So far this push has run into opposition from senior Republicans, who led the effort a decade ago to ban earmarks as both wasteful spending and part of a corrupt pay-to-play culture with lobbyists.

Rep. Nita M. Lowey (D-N.Y.), chairwoman of the House Appropriations Committee, announced that she lacked the “necessary bipartisan, bicameral” agreement to include “congressionally directed spending” — the formal name for narrow provisions lawmakers insert into bigger legislation — in this year’s spending bills. But Lowey said she would continue discussions with Republicans and Democrats.

The case study for the pros and cons of an earmark system really can be seen through the federal highway bills of the past 30 years, which are effectively smaller versions of the massive infrastructure plans Trump and Democrats talked about at the White House.

Back in the 1980s, earmarks used to be relatively limited. The federal highway bills that passed in 1982 and 1987 contained fewer than 200 total projects directed by members of Congress, but then in 1991 that figure jumped to more than 500 such earmarks.

And six years later, as Congress geared up for another big highway bill, the legendary chairman of the House Transportation and Infrastructure Committee, Bud Shuster (R-Pa.), fully unleashed the spigot. Shuster devised a formula for earmarks that doled out funds to every single lawmaker — party leaders and the top members of the committee got the largest sum, on down the line.

With almost 1,900 earmarks, Shuster steamrolled conservative opponents who thought his proposal was bloated. In 1998, he won a big bipartisan vote for a six-year highway bill: 143 Republicans and 153 Democrats.

Yes, some corruption questions arose, as federal investigators probed Shuster’s ties to a former staffer who turned into a transportation lobbyist while raising money for his political campaigns.

But by and large those earmarks were beloved.

Even the lowliest freshman in the minority got a pot worth millions of dollars. Every member of Congress effectively became the equivalent of mayor, town council and state transportation official. They attended ribbon-cutting ceremonies with oversized fake checks, telling constituents how much they were delivering, almost immediately.

By 2005, as the new highway bill got drafted, things got out of control. The new chairman, Rep. Don Young (R-Alaska), oversaw a process that included more than 5,700 earmarks worth more than $20 billion — more lawmaker projects in that one bill than Congress had approved in the previous 35 years of highway bills combined.

Not surprisingly, the bill passed overwhelmingly — 412 to 8 in the House, 91 to 4 in the Senate.

Also, not surprisingly, quite a few bad apples emerged.

Young included millions for a bridge to a barely populated town in Alaska that anti-earmark crusaders held up as the poster child for congressional excess, dubbing it “The Bridge to Nowhere.”

Young found himself under investigation regarding a highway interchange earmark that developers in South Florida sought but local officials opposed. This came as corruption investigations for other earmarked projects landed three congressmen and dozens of other former staff and lobbyists in prison.

In 2006, Democrats ran on a “drain the swamp” message and, in the majority in 2007, they created a transparent process: Lawmakers had to disclose their earmark requests and certify there were no conflicts of interest.

Even that step, however, revealed what had become an access-driven process: Staffers to key lawmakers would set up lobbying shops based on getting earmarks from their former boss for their clients.

So Republicans, taking over the House in 2011, ended earmarks altogether. It definitely made Congress a more ethical place, but over time lawmakers realized they did not have the same level of buy-in on big legislation anymore.

Government shutdowns, once unthinkable because lawmakers had so many of their own earmarks in the appropriation bills, have become commonplace.

And the highway bill is no longer a sure thing. In 2012, with no earmarks to dole out, Congress could agree on only a two-year bill, and in late 2015, after bitter fights, lawmakers signed off on a five-year highway bill.

The question now is: If earmarks come back, what restrictions should apply?

One key provision should be eliminating lobbyists from the process. All the earmark corruption cases included a lobbyist trying to grease the process with money flowing in every direction.

Any system that restricted lobbyists from working for earmarks would be cleaner and easier to justify.

Imagine if Trump and Congress agreed to even a $1 trillion infrastructure plan and devoted 5 percent of the funding — $50 billion — to lawmaker projects.

Every lawmaker could get roughly $50 million to devote to their districts, choosing to boost local schools or universities, or underfunded highway projects or broadband programs for low-income regions.

The lawmakers and their staffs could hold their own listening tours of districts to vet projects and make decisions. Constituents would actually see results from what their congressman delivered, as opposed to unknown federal and state officials who fund the majority of projects.

That’s the best case earmark supporters can make.

“No executive branch official knows a district and its needs better than that district’s representative,” Hoyer said.