POWER OF ATTORNEY

For Executing Forms 3, 4 and 5

Know all by these present,  that the undersigned  hereby constitutes and
appoints each John L. MacCarthy,  Gifford R. Zimmerman,  Larry W. Martin,
Kevin J. McCarthy and Mary E. Keefe, his/her true and lawful attorney-in-fact
to:

(1)       execute for and on behalf of the  undersigned  Forms 3, 4 and 5 (and
          any amendments  thereto) in accordance with the requirements  of
          Section 16(a) of the Securities  Exchange Act of 1934 and Section
          30(f) of the  Investment  Company Act of 1940 and the rules thereunder

(2)       do and  perform  any and all acts for and on behalf  of the
          undersigned  which may be  necessary  or  desirable  in connection
          with the execution  and timely  filing of any such Form 3, 4 and 5
          (and any amendment  thereto) with the United States Securities and
         Exchange Commission, the New York Stock Exchange and any other
         authority; and

(3)       take any other  action of any type  whatsoever  in  connection
        with the  foregoing  which,  in the  opinion of such attorney-in-fact,
          may be of benefit to, in the best interest of, or legally required by,
          the undersigned,  it being understood  that the  documents  executed
          by such  attorney-in-fact  on behalf of the  undersigned  pursuant to
          this Power of Attorney  shall be in such form and shall contain such
          terms and  conditions as such  attorney-in-fact  may approve in
          his/her discretion.

The  undersigned  hereby grants to each such  attorney-in-fact  full power and
authority to do and perform each and every act and thing whatsoever  requisite,
necessary and proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as such  attorney-in-fact
might or could do if personally present,  with the full power of substitute,
by virtue of  this  power  of  attorney  and  the  rights  and  powers  herein
granted.   The  undersigned   acknowledges   that  the  foregoing
attorneys-in-fact,  in  serving  in such  capacity  at the  request  of the
undersigned,  are not  assuming  any of the  undersigned's
responsibilities  to comply with Section 16 of the Securities  Exchange Act
of 1934 and Section 30(f) of the Investment  Company Act of
1940.

IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 3 day
of August 2007.


         /s/ John P. Amboian
Signature

          John P. Amboian
  Print Name

STATE OF ILLINOIS                   )
                                    )
COUNTY OF COOK                      )


On this 3 day of August 2007,  personally  appeared before me, a Notary Public
in and for said County and State, the person named above
who is known to me to be the person whose name and signature is affixed to the
foregoing  Power of Attorney and who  acknowledged  the
same to be his voluntary act and deed for the intent and purposes therein set
forth.



/s/ Jose A. Visaya
 Notary Public
My Commission Expires: 5-15-2009