On Wednesday, House Republicans caused a ruckus by abruptly yanking their $44.1 billion transportation and housing budget off the floor.

The leadership couldn't find enough votes for the bill, in part because the proposed spending cuts were too deep for virtually all Democrats and even some Republicans. Combine that with the fact that a certain number of conservatives will oppose most spending bills, period, and that spelled doom for the so-called THUD bill.

The House Republican budget would have cut Amtrak's funding by 21 percent. (Gerald Martineau/THE WASHINGTON POST)

But what did those spending cuts actually look like? And why were they too sharp even for many Republicans?

It's worth taking a step back to understand the position House Republicans had put themselves in. Rep. Paul Ryan's budget had tried to keep the sequester's discretionary spending level of $967 billion. But they wanted to give more of that money to defense, which necessitated even deeper cuts to domestic spending. That was fine in the abstract. But the THUD bill was one of the first times they had to get specific.

Here's what some of those cuts looked like in practice and why they lost so many votes:

-- Community Development Block Grant funding was cut to $1.6 billion, or 47 percent below the post-sequestration 2013 level of $3 billion. By most accounts, this was the cut that doomed the bill, repelling Democrats and some moderate Republicans. (The GOP leadership made a last-ditch effort to restore about $350 million here, to no avail.)

These grants are, essentially, a form of aid to cities. "Communities use these funds to rehabilitate affordable single-family housing, improve damaged streets, sewers and water systems in low-income neighborhoods, and provide community services to seniors and children," explains Doug Rice of the Center on Budget and Policy Priorities. Los Angeles, for instance, funds domestic-violence shelters and summer programs for kids.

The block grants also tend to be popular with mayors in districts across the country. And they've already taken a hit in recent years — states have lost $2.5 billion in total since 2010 (compared with what would have happened if spending had stayed constant). Cutting more proved to be too much.

-- Housing vouchers were kept at roughly sequester levels, or $17 billion. At first glance, this doesn't look like a cut to the nation's largest rental-assistance program. After all, funding for this program will be at $16.3 billion in 2013 (once sequestration bites down).

This one was more a concern for Democrats than Republicans. Many liberal groups had warned that the sequester cuts were already too low. CBPP estimates that the House bill would leave 100,000 low-income seniors, people with disabilities, and families with children without housing assistance, compared with last year. By contrast, CBPP estimated that the Senate bill, with about $600 million in extra funding, would bridge the gap.

-- Transportation got cut to $15.3 billion, or 15 percent below 2013 levels. The House had already agreed to spend about $50 billion in 2014 on highway and transit programs as part of the big transportation bill passed last year. But this new appropriations bill made tweaks to just about everything else.

For instance, the House budget bill would entirely eliminate the TIGER grant program, which has sent more than $3 billion to states that have competed to come up with the most beneficial transportation projects. (Republicans have complained that the Obama administration has politicized the program.)

The bill also made a slight 2 percent cut to the New Start program, which helps cities invest in things like light rail and bus rapid transit. And it cut Amtrak's budget by 21 percent. The latter, says Joshua Schank of the ENO Center for Transportation, would likely force Amtrak to slow down or hold off on planned upgrades throughout the Northeast.

Some of these cuts reflect the fact that Republican voters are increasingly concentrated in rural and suburban areas, while Democrats tend to be clustered in cities. That might help explain why the Republican budget tended to cut transit programs while leaving key highway programs alone. (The National Highway Traffic Safety Administration, for instance, got a small 1 percent cut in spending.) But many of these programs tend to spread money across districts all over the country.

Are there any other options? Right now, the Senate is debating its own THUD bill, which would set spending for housing and transportation at pre-sequestration levels — or about $54 billion for next year, about $10 billion higher than the House bill. The problem is that this bill is already getting filibustered by Republicans. And it likely won't prove popular with the House GOP, either.

Rep. Hal Rogers, the Republican chairman of the House appropriations committee, has said that the chances for the House THUD bill, with its unpopular cuts, are "bleak at best." But he also thinks the higher spending levels of the Senate bill “are also simply not achievable in this Congress.” That won't make it easy to find a compromise.