I mean the Congress under the Articles of Confederation from 1781 to 1789. Did the Constitutional system sweep aside the former class of politicians who made a poor job of government under the Articles and replaced them with a new group? Or did the two groups overlap significantly?
There is two questions here, since "political elite" did not (and does not) equate to membership in congress. In terms of the physical overlap of the two Congresses, let's examine the composition of the First United States Congress.
In the Senate, only four senators out of 25 (+3 replacements), or 16% (14.3% counting replacements) had not previously served in the Continental or Confederation Congresses:
- Richard Bassett, Delaware state legislator
- William Maclay, Pennsylvania state legislator
- Theodore Foster, Rhode Island state employee and brother-in-law of Governor Arthur Fenner
- Joseph Stanton Jr, commander of the Rhode Island militia and assembly representative
In the House of Representatives, only 29 out of 68 representatives, or 43% (including 1 replacement) were not also a previous delegate to the Continental or Confederation Congresses:
- Jonathan Trumbull Jr, brother of delegate Joseph Trumball and son of the Connecticut Governor
- James Jackson, Georgia state legislator and governor.
- George Mathews, Georgia state legislator and govenor
- Michael Stone, brother of delegate Thomas and Maryland Governor John Hoskins Stone
- George Gale of Maryland
- Fisher Ames, Massachusetts state legislator
- Benjamin Goodhue, Massachusetts state legislator
- George Leonard, Massachusetts state legislator
- Jonathan Grout of Massachusetts
- Thomas Sinnickson, New Jersey state legislator
- Peter Silvester, New York judge
- Jeremiah Van Rensselaer of New York
- John Steele, North Carolina state legislator
- John Sevier, governor of the State of Franklin and future founding father of Tennessee
- Thomas Hartley of Pennsylvania
- Daniel Hiester, Pennsylvania state legislator
- Peter Muhlenberg, Vice President of Pennsylvania and brother of delegate Frederick Muhlenberg
- Thomas Scott, Pennsylvania state legislator
- Benjamin Bourne, Rhode Island state legislator
- William Loughton Smith of South Carolina
- Aedanus Burke, cousin of North Carolina governor Thomas Burke
- Alexander White, Virginia state legislator and brother-in-law of governor James Wood
- Andrew Moore, major general of the Virginia militia
- Richard Bland Lee, Virginia state legislator and son of state senator Henry Lee II
- Issac Coles, Virginia state legislator
- John Page, Virginia state legislator and Lieutenant Governor
- Josiah Parker of Virginia
- Samuel Griffin, Virginia state legislator and brother of Cyrus, President of the Continental Congress
- William Branch Giles of Virginia
More previous delegates were elected to later Congresses, but for obvious reasons I am not going to bother with them. By these results alone, we can confirm that the two memberships overlapped to a very high degree.
In terms of continuity, I will contend that there is no "two groups" to speak of - that the exact same class of political elites continued in power. Referring back to the previous list, it is readily discernible that the vast majority of new members were were previously state legislators. Almost all of them were well connected to the political establishment in general. They already did belong to the political elite.
That more of the movers and shapers of politics migrated to the federal centre after the United States centralised with the Constitution is not surprising. In this they were also aided by the fact that the new United States Congress had almost twice as many seats as the Congress of the Confederation had.