Post-election jubilation among Democrats last fall as they achieved huge House and Senate majorities is melting into the reality of governing during the dog days of summer.

The House has already departed Washington to begin its summer recess. The Senate’s break is set to begin on Friday, August 7.

Each chamber has missed the deadline set by President Barack Obama to pass health care reform bills before leaving town for their summer getaways. The delay can be attributed in part to Republican resistance and to fissures within the Democratic Party.

In order to achieve their majorities, Democrats wisely extended their tent. The head of their House campaign arm in 2006—Rahm Emanuel, who is now White House chief of staff—recruited moderates who could win conservative-leaning districts. Many of those victors became members of the Blue Dog Coalition.

Now the Blue Dogs are barking on health care legislation. Several of them who sit on the House Energy and Commerce Committee were successful in getting the panel to include amendments that would lower the cost of the measure and allow negotiated reimbursement rates in a government-run insurance option, rather than setting them based on Medicare rates.

Their intervention inflamed House progressives—formerly known as liberals. Just before the House broke for recess, 57 members of the Congressional Progressive Caucus sent a letter to House Speaker Nancy Pelosi, D-California, asserting that the Energy and Commerce agreement would reduce subsidies for the poor and middle class.

“In short, this agreement will result in the public, both as insurance purchasers and as taxpayers, paying ever higher rates to insurance companies,” the letter states.

Moderate and liberal Democrats will now have to wrestle a final House bill to the ground. The commerce, labor and tax committees have approved measures with varying kinds of employer mandates and public options.

In a July 30 press conference, which was held outdoors despite 90-degree temperatures and high humidity, leaders of the progressive Democrats warned that they would oppose what they called a watered-down bill.

“We want a plan with a meaningful public option,” said Rep. Lynn Woolsey, D-California and a former HR professional. “We can compromise no more.”

She and her colleagues were occasionally drowned out by protestors chanting for a single-payer government health care system. Some progressives support such a plan, but congressional leadership has ruled it out. Nonetheless, opponents of the public option call it the first step on a slippery slope to government-run health care.

Over in the Senate, health care reform also is in flux. The health committee has approved a bill with an employer mandate and a public option, while the Finance Committee is trying to cobble together a bill with bipartisan support that would jettison each idea.

Reconciling those two bills—once Finance has introduced and approved its version—is going to be a big challenge, if Democrats want to attract more than token GOP support and ensure that their own moderates stay on board.

The rising tension was illustrated in a July 30 Senate press conference. Majority Leader Harry Reid, D-Nevada, dropped all senatorial courtesy in answering a question posed by my Crain Communications colleague Matthew DoBias of Modern Healthcare.

DoBias asked a legitimate question: How will the two Senate committees be able to bridge the differences between divergent bills? The answer, which will unfold over the fall, may determine the outcome of health care reform.

Reid took umbrage. “With all due respect,” Reid said, pausing and casting an icy stare at DoBias, “you don’t know what you’re talking about. These are not two separate products.”

But then Reid seemed to endorse the premise of DoBias’ query with the rest of his answer about how he is going to merge the bills.

“I’m going to do it very carefully, recognizing we have to have 60 votes,” Reid said. “I’d like to have a few more than that.”

There are a total of 60 Democrats in the Senate, just enough to overcome a filibuster. Getting that number of votes—and 218 in the House—will be as much a test of Democrats’ ability to line up their colleagues as it is to attract Republicans.