Chicago Transit Authority riders finally are seeing the first fruit of the $1 billion program announced last year to fix up stations and rebuild portions of the track along the CTA's Red Line.

The big investment — the first of this magnitude in many decades — will buy the agency some time in replacing a heavily used embankment structure that originally was constructed as much as 112 years ago. Even better, it's literally taking the stink out of some of those decades-old stations.

But the struggle really has just begun to lure the additional billions of dollars the CTA needs to finish the job, and to extend the Red Line south from 95th Street into dramatically underserved areas.

The prognosis is mixed.

The CTA and its friends were able to pull some strings and insert some highly favorable clauses in the new multiyear federal surface transportation bill that finally got out of Congress earlier this summer. And it's hoping for some big help from the private sector — in particular, from an upcoming report by New York-based investment bank Goldman Sachs Group Inc., which the CTA recently retained to review its options.

But another part of the Red Line story was being written in Tampa, Fla., where the Republican National Convention just wrapped up. Depending on who wins the presidency and control of Congress this fall, tapping that new federal transit bill for big cash could be much, much harder.

First, the good news.

According to both the CTA and congressional sources, the new federal transit bill, known as MAP-21, has at least three different clauses that should boost Red Line work.

In fact, says CTA President Forrest Claypool, “Without that (bill), Red Line modernization would be impossible.”

The first clause boosts the amount of money the CTA gets every year from the feds for infrastructure work. The exact hike isn't yet known, but it apparently is $15 million to $25 million a year.

That sounds pitifully small compared with the $2 billion to $5 billion the CTA will need to rebuild the north end of the Red Line, depending on which option it selects, and the $1.4 billion needed to extend the line south to Chicago's city limits. But that money can be used as a revenue stream to finance at least 10 times more in bonds. So $25 million could get the CTA a quarter of a billion dollars in one chunk upfront — a good starting point.

The really big money, though, is in the “new start” clause of the bill. Specifically, it sets aside $3.8 billion over the next two years to pay for projects all over the country.

Now, “new start” implies building something new, rather than replacing something old. And that's traditionally how the program has worked, though U.S. Sen. Dick Durbin, D-Ill., and then-Rep. Rahm Emanuel were able to get through a special earmark a few years ago to pay for the reconstruction of the Brown Line.

But MAP-21 gives older systems a new way to tap new-start money: All they have to show is that, as a result of the proposed work, the “core capacity” of the bus or train line involved would increase at least 10 percent.

That's a pretty low bar. The preliminary rules on how the new new-start money will be allotted won't be released until October, but you can bet your fare card that the CTA will do what it can.

Oddly, Metra, which garnered a ton of new-start money in prior funding cycles, doesn't have anything cooking right now. More on that another time.

Then there's a third clause in the new bill that would help the CTA. It's a loan program, known as TIFIA — for the Transportation Infrastructure Finance and Innovation Act — that allows transit agencies to borrow funds for as long as 35 years at an interest rate as low as 2.5 percent. And the amount that can be borrowed is as much as 30 times the available repayment revenue stream.

TIFIA funding is way up in the new bill, with $750 million this fiscal year and $1 billion in 2014. At a borrowing/revenue-stream ratio of 30-to-1, the CTA wouldn't need a lot to get a lot.

Of course, there has to be a repayment revenue stream: fares, a local tax-increment financing district or some private money. That's one of the reasons the CTA hired Goldman, to sniff out potential private investors, though it's more likely that private cash would be used to guarantee against construction cost overruns, rather than to finance the project.

Now, the bad news.

If Barack Obama has done anything for his hometown, it has been to load up the U.S. Department of Transportation with lots and lots of folks from Illinois, from department Secretary Ray LaHood to Dorval Carter, a former CTA exec who now is general counsel of the Federal Transit Administration, which awards new-start and TIFIA funds.

All of those folks have to operate within the rules. But within the maze of the federal bureaucracy, it's always good to have friends. And if those friends go after the next election, Chicago will lose some influence in the writing of new MAP-21 rules and the awarding of new MAP-21 funds.

Beyond that, the “new start” money has yet to be appropriated by Congress, and a GOP White House and Congress almost certainly would make roads and Sun Belt transit projects a higher priority than helping Mr. Obama's hometown.

Only this spring, the GOP-controlled House tried to eliminate the share of federal gasoline taxes that goes to transit, and while the effort was beaten back — with the help of suburban GOP congressmen such as Bob Dold and Judy Biggert — hostilities could resume at any time.

One imponderable is whether Mayor Rahm Emanuel's new infrastructure bank will somehow come up with funds. Maybe, but no one is saying much about that yet.

My best bet is that, little by little, this job will get funded. The Red Line is the core of the CTA's system and critical to Chicago's health. But it's likely to come in bits and pieces. And it could take a while – quite a while.